The proposed research is a continuation of a long-term project dedicated to the understanding of how tactile information is represented in the cerebellar cortex and nuclei as conveyed by the climbing fiber system. The proposed studies of the cerebellar cortex will examine the climbing fiber organization in lobule VII, the lateral cortex of the anterior lobe, and the flocculus in anesthetized cats. These studies will include multiple microelectrode penetrations in each animal, extracellular unit recording of a large population of Purkinje cells, and tactile stimulation of the body surface. For each climbing fiber response isolated, the following parameters will be examined: modality of the stimuli, receptive field characteristics, and location of the response. The proposed studies of the nuclear neurons will involve extracellular recording within the anterior interpositus nucleus (NIA) in anesthetized or decerebrated cats. A criterion will first be developed for the identification of climbing fiber mediated excitatory and inhibitory activity of the interpositus neurons. Various parameters of the tactile stimulation will be evaluated in conjunction with electrical stimualtion or inactivation of the inferior olivary complex. A final study will involve a detailed mapping of the NIA to reveal the proportional and spatial organization of the climbing fiber mediated representations of the body surface. An analysis of the receptive fields obtained from the cortical and NIA studies will be used to develop a mathematical model of the climbing fiber representation. An attempt will be made to determine how skin location information is encoded in different cortical regional and in the nuclear neurons. The proposed studies of the climbing system will provide (1) a completed description of the spatial distribution and proportional representation of the body surface throughout the cerebellar cortex, (2) information on how location of a stimulus point on the body surface is encoded in various cortical regions, (3) an indication of the type and extent of convergence of information from the Purkinje cells to the NIA neurons, and (4) insights on the degree of congruence of Purkinje cell and collateral inforamtion at the nuclear level. These proposed studies will permit the formulation of new therories of cerebellar function